We wish to extend the exploration of diffusive processes in multicomponent solute systems which are coupled by chemical reactions. These systems will include proteins undergoing chemical reactions affecting their diffusion, which reactions may be mediated by the binding of specific ligands. Such systems diffuse non-ideally. The diffusion of the macromolecular system, which is readily observable with an interferometric optical observation system, such as that of the Gouy diffusiometer, then causes differential transport of ligand, and generates a gradient of concentration of the ligand, even though none was originally present. This generated ligand concentration gradient then in turn exerts a feedback control which determines, via the influence of ligand binding on the macromolecular reaction, the overall diffusion behavior of the system. The non-ideality of the macromolecular diffusion can be measured precisely by the Gouy method, and translated into descriptions in terms of crossed-diffusion coefficients. Reasonable models can also be used to develop via computers a predicted non-ideality, which can be compared directly with experiment. It is felt that this type of study can provide basic information on the nature of ionic and other complex feedback transport phenomena in physiological systems. As metabolic pathways involve molecular encounters in multiply coupled reactions, such transport is an integral part of the mechanism of metabolism.